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Fred Hebard wrote (a quote from Wharton & Field's):
> For these observations in an artificial horizon, Wharton recommends an
> eypiece shade rather than the swing-out sextant shades. He also
> recommends multiple eyepiece shades of varying optical density. He
> discusses examination of errors caused by swing-out sextant shades.
>
Robert responds,
I don't know if I buy the bit about swing out sextant shades introducing
errors. Perhaps this was true back when that book was written, however can
the same be true for modern sextant shades?